400EX won't shift

[K400EX&A250EX]

My son's 400EX is stuck in 3rd gear and won't shift either up or down. The engine runs fine, and 3rd gear appears to be fine (we were able to make it back to camp from the middle of the dunes)...but the bike just won't shift at all. I will likely have to take it to the shop regardless, but I just wanted to know what you guys think may be causing it...and whether a fledgling mechanic like myself (with basic tools and the Honda Service Manual) might be able to fix it. I'm not totally clueless when it comes to fixing things...but I'm FAR from an experienced mechanic. Any help would be much appreciated.

[Aceman]

Is the shifter bent and caught on anything preventing it from shifting? If your alright there, then I would assume your shift forks are somehow bound up inside your motor. You will need to tear your engine apart to find out exactly what is wrong. If your willing to learn and have the patience and the tools to tear your engine apart, I say go for it. You'll learn a lot and save a ton of money all at the same time. You'd get raped by the dealer if you had them tear it down for you. What I would do is read the sections in the manual about engine dissassembly and see if it is something you could do. Patience and attention to detail are what get you through an engine teardown.

its prolly not the shifter. but check and see if it sliped off the splines or sumtin just to rule that out. but i bet its your forks in ur tranny. ive seen alot of people blow transmissions in the dunes. Maybe because it has so much more friction or sumtin and it takes more to go cuz they say sand robs hp.

[gopeddin400EX]

will the shift lever even move, and if it does, does it feel like its going all the way down or is it like when your in first and try to kick it down?

[K400EX&A250EX]

The shifter seems to have a full range of motion, but it just doesn't "catch" internally and shift the gears. It is not bent, caught on anything, or anything external. It just moves smoothly to the bottom and top of its range of motion but doesn't actually shift.

I took a look through the service manual last night, and I'm pretty sure I'm taking it to the shop. I have a shop I trust. I'm sure it will still be expensive just given the amount of work it will take, but I trust him to be fair. I'm afraid if that if I try fixing it myself I may NEVER get it back together.